Forced air distribution systems are commonly used to heat or cool homes. There is generally a furnace to supply heated air or an air conditioning unit to provide cooled air to regions a home via ducts. In many cases, the furnace or air conditioning unit is located in the basement of the home and duct work extends from the basement to terminate at an opening or port in the floor or wall of a room to deliver cooled or heated air to the room. To reduce costs and the complexity of the installation, most forced air distribution systems are controlled by a single thermostat that is centrally located. A user sets the thermostat to a desired temperature which turns on the furnace or air conditioning unit to deliver air through the duct work to the various rooms. When the desired temperature is reached at the thermostat, the furnace or air conditioning unit is switched off by the thermostat. The obvious problem with this arrangement is that while the desired temperature may be reached at the thermostat, this is no guarantee that the desired temperature is reached throughout all the rooms of the home. A single thermostat cannot provide room-by-room temperature control. To address this problem to a limited extent, each port is generally fitted with a register which includes a valve system, often pivotable flaps, that can be set to a particular position to partially control the flow of air into a room. The registers tend to be adjusted to a single position and left as it is a time consuming task to adjust the registers throughout a home.
To combat this problem, the industry has responded with various “multi-zone” climate control systems typically with from 2 to 4 zones per home, each zone controlled by its own thermostat. This system typically adds $2-5,000 to installation costs, and still is only a partial solution. For example, if all the bedrooms of a home are on a single thermostat, the occupants of the other rooms have no individual control of their room's temperature. “Multi-zone” climate control systems are only practical in new construction as they tend to require extensive reworking of the heating and cooling ducts. Retrofitting existing homes can take in excess of 3 weeks to complete.
Electric baseboard heaters are available as a substitute solution, allowing separate control for each room, but, not only are they very expensive to operate, but also slow to heat a room. Retrofitting an existing home with electric baseboard heaters requires upgrading the home's electrical service, and ripping up walls and floors to install the wiring, a costly and time consuming installation. With new construction, these costs are partly avoided, however, the cost of operation, and “slowness” still remain.
Radiant heating, using hot water or electrical elements in walls, floors or ceilings use separate thermostats or controls for each room, but, are also expensive to install and operate, slow to heat required areas, plus require costly control systems. Hot water radiant heating requires a boiler to heat the water, and a complex series of“zone valves” to control the flow of heat where required. Both these systems are installed into floors, walls or ceilings requiring major renovations or new construction to be viable.
Heat pumps use a large refrigeration system “run in reverse” to heat air, and have the added advantage that by “reversing the operation” can be used for air conditioning also. Heat pumps though inexpensive to operate, present an initial installation cost often many times higher than alternate systems. To operate heat pumps for several zones requires a separate heat pump and thermostat for each zone, or installation of the conventional multi-zone systems discussed above, greatly increasing the installation costs.
In view of the foregoing discussion, it is apparent that there is a need for an alternative system for controlling the distribution of air through the existing duct system in a home which is able to control temperature on a room by room zone basis and which is relatively inexpensive to operate and install.